Group 1 Elements

Thomas slag is also called as phosphatic slag. It is a mixture of calcium phosphate and calcium silicate. It is used as manure. Chemically it is

On heating above and all is obtained as:

Alkali metal halides have high melting point. The melting points of alkali metal chloride decreases from NaCI to CsCl. (except Li).

So, NaCI has highest melting point and CsCl has lowest melting point.